The present invention relates to a substrate processing system for forming a film such as an interlayer insulation film, an interface apparatus used in the system, and a substrate transportation method.
In the process of manufacture of semiconductor devices, in general, a predetermined circuit pattern is formed on a surface of each substrate to be processed, for example, a semiconductor wafer or the like, by using photolithography technique. Meanwhile, with recent improvement in the integration of semiconductor devices, more and more circuit patterns have come to be formed in layers, and in such a multilayer wiring structure, it is essential that irregularities of a lower wiring should be as small as possible. Studies have therefore been focused on techniques of flattening an interlayer insulation film for insulating a lower wiring from an upper wiring.
As a conventional method for flattening an interlayer insulation film, a method using SOG (Spin On Glass) is known. In the SOG application method, a processing solution (SOG solution) containing a silanol compound such as Si(OH)4, which is a constituent of a film to be obtained, mixed in ethyl alcohol or the like as a solvent is applied to a wafer, which is a substrate to be processed, and the wafer is subjected to a heating process to allow the solvent to evaporate and advance the polymerization reaction of the silanol compound, thereby forming an insulation film.
More specifically, a wafer is placed on a spin chuck, and with the wafer rotated at a rotational speed of 2000 to 6000 rpm, the SOG solution is made to drip onto the wafer so that the solution may be applied to the wafer, thereby forming an SOG film. Subsequently, the SOG film is subjected to a preheating process at 100 to 140.degree. C. to evaporate the solvent, and then further to a heating process at a temperature of about 400.degree. C. so that the silanol compound forming the SOG film may be polymerized by means of siloxane bonds. In cases where SOG films are to be formed in layers, the step of applying the SOG solution to a wafer and evaporating the solvent is repeated and then the wafer is subjected to the heating process, or the step of applying the SOG solution to the wafer and evaporating the solvent and the heating process are repeatedly carried out.
A coating apparatus for applying the SOG solution to surfaces of wafers employs a spin coating method wherein, with a single wafer rotated as stated above, the SOG solution is made to drip onto the wafer surface so that the solution may be spread over and applied to the wafer. Thus, wafers are coated with the SOG solution one by one according to so-called single wafer processing.
In a heating apparatus for subjecting wafers to a heating process after the application of the SOG solution, on the other hand, batch process is employed in view of operating efficiency wherein a plurality of wafers are held by a wafer boat and the wafer boat is transported into a heater to subject the wafers collectively to the heating process.
Thus, the application of the SOG solution, which is single wafer processing, and the heating process, which is batch processing, need to be carried out with the use of respective different apparatuses, and therefore, an interface apparatus is provided for transporting semiconductor wafers applied with the solution by the application apparatus to the heating apparatus.
In the interface apparatus, plural wafers, which have been transported one by one from the application apparatus, are placed one over another in a boat, and the boat carrying the wafers is conveyed into the heating apparatus by a transporting arm of the heating apparatus.
In the heating apparatus, the plural wafers are subjected to a heating process together with the boat, and after the heating process, the wafer boat carrying the wafers is returned to the interface apparatus by the transporting arm of the heating apparatus.
The interface apparatus has a stationary stage provided therein for permitting a plurality of boats to be placed thereon side by side, and is constructed such that before and after the transportation of each boat to and from the heating apparatus, the boat is placed exactly at a reference position on the stationary stage.
Occasionally, however, the boat is placed with shift position in a direction of rotation (circumferential direction) displaced from the reference position, and in this case an alarm is issued. If this occurs, the operator must correct the circumferential position of the boat; however, this operation is complicated.